I. Field of the Invention
The present invention relates to a mechanical part having a wear-resistant surface which is brought into contact with a member selected from the group consisting of paper, rubber, plastics, resin, ceramics, and metal.
II. Description of the Prior Art
As is known, since iron and steel have superior mechanical properties, such as strength, ductility, toughness, hardness, and the like, to other metals, they are used for a machine material, structural material, and the like as the most basic material.
Iron and steel can be classified into iron, steel, and cast steel in accordance with their carbon contents. Furthermore, steel can be classified into carbon steel and alloy steel that is obtained by adding various elements to the carbon steel to provide specific characteristics. They are used for various applications in accordance with their characteristics.
Mechanical or structural parts consisting of steel must have required characteristics in accordance with conditions of use or environmental factors, in addition to the mechanical strength. When parts consisting of steel are used while being brought into frictional contact with other parts, a wear-resistance and a surface smoothness are required. For example, when parts, like bearing parts or sliding parts of a machine, are brought into frictional contact with each other, or when tools are brought into contact with other parts, the wear-resistance and the surface smoothness are required in order to prevent the wear of parts and to improve the sliding properties against other parts. When steel parts are used in a corrosive environment such as water, acid, alkali, and the like, for example in the case of a shaft or impeller of a submersible pump, a high resistance to chemicals is required.
In recent years, attempts have been made such that a surface layer which is different from a substrate is formed on the surface of parts, so that required characteristics according to conditions of use or environmental factors are provided to parts consisting of steel, in addition to the original characteristics of their material. Such a surface layer must have a wear resistance to friction with other parts and smoothness for improving sliding properties against other parts, must not damage other parts, and must have a resistance to chemicals high enough not to be corroded in a corrosive environment. Furthermore, the surface layer must be formed on the substrate surface of the parts with high mechanical strength, will not degrade characteristics of the substrate upon formation, and needs no finishing such as grinding after formation.
As a method for forming a surface layer on a substrate surface of parts consisting of iron or steel, plating, PVD (physical vapor deposition), CVD (chemical vapor deposition), frame spraying, and the like are known. However, these methods cannot always satisfy all the above-mentioned requirements, and practical application is not easily accomplished. More specifically, surface layers formed by these methods have insufficient denseness, wear-resistance, and smoothness. A bonding strength between the surface layer and the substrate is also insufficient, and the surface layer is often peeled from the substrate. In addition, a finishing process is required after the formation of the surface layer.